The present invention relates to an apparatus and method for handling and installing a subsea flowline jumper. More particularly, the invention relates to an apparatus and method for offloading the jumper from a vessel in the horizontal position and then rotating the jumper into the vertical position for installation on two items of subsea equipment.
Flowline jumpers are used in the field of subsea oil and gas production to provide fluid communication between two items of subsea equipment. For example, a flowline jumper may be used to connect the production outlet of a christmas tree to the end of a subsea pipeline that terminates near the christmas tree. Thus, a flowline jumper usually comprises a length of conduit and two fluid couplings, one located at each end of the conduit, which are adapted to mate with corresponding receptacles connected to the subsea equipment. In addition, to facilitate installing the flowline jumper from a surface vessel, the receptacles connected to the subsea equipment are oriented vertically upward and the flowline jumper is constructed so that the conduit and the fluid couplings lie in a single plane with the fluid couplings oriented in the same direction. In this manner, the flowline jumper may be lowered vertically from the surface vessel and the fluid couplings simply landed on the receptacles.
In order to lower the flowline jumper vertically from the vessel, it must first be lifted from the transport vessel into the vertical position. This requires that the flowline jumper either be transported in the vertical position or transported in the horizontal position and then lifted into the vertical position prior to installation. However, flowline jumpers are typically long, bulky and relatively heavy devices. Thus, transporting the flowline jumper in the vertical position usually requires the use of large, expensive vertical shipping frames and fixtures. But, lifting the flowline jumper into the vertical position from the horizontal position increases the risk that the fluid couplings will impact with the boat and be damaged during the critical liftoff operation.
The present invention overcomes these problems by providing a flowline jumper handling apparatus for lifting a flowline jumper from a surface vessel in a generally horizontal position and then lowering the flowline jumper to a subsea structure in a generally vertical position, the handling apparatus comprising an elongated spreader bar, at least one first cable connecting the spreader bar to the subsea jumper, at least one second cable connecting the spreader bar to a first lifting apparatus located on the surface vessel, at least one through member connected to the spreader bar or to the second cable, at least one third cable passing through the through member and connecting the flowline jumper to a second lifting apparatus located on the surface vessel, and a restricting member connected to the third cable between the flowline jumper and the through member for preventing the third cable from passing through the through member, wherein as the third cable is lifted the restricting member will engage the through member and lift both the spreader bar and the flowline jumper, wherein the length of the third cable between the flowline jumper and the restricting member and the lengths of the first and second cables are selected to maintain the flowline jumper in a generally horizontal position as the third cable is lifted, and wherein the flowline jumper is allowed to rotate from the generally horizontal position to a generally vertical position by releasing the third cable, whereby the subsea jumper may be lifted in the generally horizontal position by the second lifting apparatus and then lowered to the subsea structure in the vertical position by the first lifting apparatus.
The present invention also comprises a method for offloading a flowline jumper from a surface vessel in a generally horizontal position and then lowering the flowline jumper to a subsea structure in a generally vertical position, the method comprising the steps of connecting the flowline jumper to a first lifting apparatus, connecting the flowline jumper to a second lifting apparatus, lifting the flowline jumper from the vessel in the generally horizontal position with the first lifting apparatus, supporting the flowline jumper with the second lifting apparatus, releasing the flowline jumper from the first lifting apparatus to thereby allow the flowline jumper to rotate from the generally horizontal position to the generally vertical position, and lowering the flowline jumper to the subsea structure with the second lifting apparatus.
Thus, the present invention allows the flowline jumper to be transported to the installation site in the horizontal position, eliminating the need for expensive vertical shipping frames and fixtures. In addition, the present invention permits the flowline jumper to be lifted off of the transport vessel in a horizontal position and then rotated to the vertical position, for example after it has been moved away from the transport vessel. This reduces the possibility that the flowline jumper will be damaged as it is being lifted off of the transport vessel.
These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings. In the drawings, the same reference numbers are used to denote similar components in the various embodiments.